The preamble may contain any C code, including function and variable
declarations and definitions. These may then be referred to from Go
code as though they were defined in the package "C". All names
declared in the preamble may be used, even if they start with a
lower-case letter. Exception: static variables in the preamble may
not be referenced from Go code; static functions are permitted.

</pre>

<p>
For backward compatibility, an imaginary literal's integer part consisting
entirely of decimal digits (and possibly underscores) is considered a decimal
integer, even if it starts with a leading <code>0</code>.
</p>

<pre>
0i
0123i         // == 123i for backward-compatibility
0o123i        // == 0o123 * 1i == 83i
0xabci        // == 0xabc * 1i == 2748i
0.i
2.71828i

	if len(s) > len(b) {
		f.err = ErrFieldTooLong
	}
	copy(b, s)
	if len(s) < len(b) {
		b[len(s)] = 0
	}

	// Some buggy readers treat regular files with a trailing slash
	// in the V7 path field as a directory even though the full path
	// recorded elsewhere (e.g., via PAX record) contains no trailing slash.
	if len(s) > len(b) && b[len(b)-1] == '/' {
		n := len(strings.TrimRight(s[:len(b)-1], "/"))

Antarctica/Casey Antarctica/Davis Antarctica/DumontDUrville Antarctica/Macquarie Antarctica/Mawson Antarctica/McMurdo Antarctica/Palmer Antarctica/Rothera Antarctica/South_Pole Antarctica/Syowa Antarctica/Troll Antarctica/Vostok Arctic/Longyearbyen Asia/Aden Asia/Almaty Asia/Amman Asia/Anadyr Asia/Aqtau Asia/Aqtobe Asia/Ashgabat Asia/Ashkhabad Asia/Atyrau Asia/Baghdad Asia/Bahrain Asia/Baku Asia/Bangkok Asia/Barnaul Asia/Beirut Asia/Bishkek Asia/Brunei Asia/Calcutta Asia/Chita Asia/Choibalsan Asia/Chongqing...

}

// alignSparseEntries mutates src and returns dst where each fragment's
// starting offset is aligned up to the nearest block edge, and each
// ending offset is aligned down to the nearest block edge.
//
// Even though the Go tar Reader and the BSD tar utility can handle entries
// with arbitrary offsets and lengths, the GNU tar utility can only handle
// offsets and lengths that are multiples of blockSize.

			Typeflag: '2',
			PAXRecords: map[string]string{
				"linkpath": "PAX4/PAX4/long-linkpath-name",
			},
			Format: FormatPAX,
		}},
	}, {
		// Both BSD and GNU tar truncate long names at first NUL even
		// if there is data following that NUL character.
		// This is reasonable as GNU long names are C-strings.
		file: "testdata/gnu-long-nul.tar",
		headers: []*Header{{
			Name:     "0123456789",
			Mode:     0644,

		tgo := t.Go
		size := t.Size
		talign := t.Align
		if f.BitOffset > 0 || f.BitSize > 0 {
			// The layout of bitfields is implementation defined,
			// so we don't know how they correspond to Go fields
			// even if they are aligned at byte boundaries.
			continue
		}

		if talign > 0 && f.ByteOffset%talign != 0 {
			// Drop misaligned fields, the same way we drop integer bit fields.

enabling the HTTP/2 use by the HTTP client broke programs
connecting to servers with buggy HTTP/2 implementations.
These kinds of changes are unavoidable and
[permitted by the Go 1 compatibility rules](/doc/go1compat).
Even so, Go provides a mechanism called GODEBUG to
reduce the impact such changes have on Go developers
using newer toolchains to compile old code.

A GODEBUG setting is a `key=value` pair

The actual name is semantically irrelevant but should be used to document
the argument's name.
It is worth stressing that <code>FP</code> is always a
pseudo-register, not a hardware
register, even on architectures with a hardware frame pointer.
</p>

<p>
For assembly functions with Go prototypes, <code>go</code> <code>vet</code> will check that the argument names
and offsets match.

	needUSize := f.UncompressedSize == ^uint32(0)
	needCSize := f.CompressedSize == ^uint32(0)
	needHeaderOffset := f.headerOffset == int64(^uint32(0))

	// Best effort to find what we need.
	// Other zip authors might not even follow the basic format,
	// and we'll just ignore the Extra content in that case.
	var modified time.Time
parseExtras:
	for extra := readBuf(f.Extra); len(extra) >= 4; { // need at least tag and size